Russia said a US investigation into the alleged collusion between some American and Russian officials to influence last year’s US presidential election is a domestic affair for Washington, and it is hurting relations between the two countries.

“We are still bewildered at the ongoing investigation. This is definitely a US domestic affair, but in this case it naturally hurts our bilateral relations, which is regrettable," Peskov noted.

He also said US President Donald Trump’s statement about the failure of the federal investigation over suspicions of Russian interference in the US election spoils the image of the US and so the investigation should be halted.

The investigations into Russia’s alleged interference in the 2016 US presidential election is led by the US Justice Department’s Special Counsel Robert Mueller and several US congressional committees.

In May, US Attorney General Jeff Sessions appointed Mueller as the special counsel after Trump fired FBI Director James Comey, who was leading the federal investigation into possible Russia collusion.

Trump has repeatedly denied allegations that his campaign colluded with Russians and has condemned the investigations. Russian President Vladimir Putin has also denied the allegations.

Donald Trump believes Special Counsel Robert Mueller ‘will be fair’ to him in the investigation into possible ties between the Trump campaign and Russia.

In a wide ranging interview on Thursday with The New York Times, Trump said he believes Mueller ‘will be fair’ to him in the probe. Trump has threatened to fire Mueller in the past.

“There’s been no collusion. But I think he’s going to be fair,” Trump said at his golf club in West Palm Beach, Florida.

Trump also said it was ‘too bad’ that Sessions recused himself from the Russia probe, the initial step that led to Mueller’s eventual appointment as special counsel.

A poll released earlier this month by The Associated Press shows that two-thirds of Americans disapprove of Trump's response to the Russia investigations.

Four in 10 think Trump has done something illegal when it comes to Russia, while three in 10 say he's done something unethical.